This invention relates to a system for distributing a fluid, comprising a fluid distribution conduit, a fluid inlet and a plurality of closeable fluid outlet branches, the distribution conduit being provided with a plug which can be propelled in response to the fluid pressure and is able to interact with a valve of an outlet branch, as disclosed in U.S. Pat. No. 4,085,769.
The known distribution system is used for distributing a gas or a liquid by means of valves arranged along the distribution conduit and which are connected with outlet branches adapted to irrigation purposes. For a relatively large area of soil, only a relatively small quantity of fluid is available per unit of time in this known system, as a simultaneous supply of fluid to all the outlet branches would cause each outlet branch to receive an insufficient quantity of fluid, the danger even existing of all the fluid flowing through the first outlet branches, so that the remaining outlet branches will be deprived of any fluid.
In the known system there is provided a plug having radially projectable parts which is propelled by the fluid until it engages a sleeve of a valve and subsequently opens the valve by a displacement of the sleeve, with the plug remaining therein in response to the fluid pressure, so that an outlet branch receives all the fluid supplied by the distribution conduit. The plug includes a built-in time relay causing radially projecting parts of the valve to be retracted after a given period of time, so that the plug can be removed from the sleeve of the valve in response to the fluid pressure in the distribution conduit and will then advance to the successive valve of a next outlet branch. A pressure drop occurring in the fluid at the plug at this moment, as the plug is being propelled ahead of the fluid, will stop the action of the time relay, so that the displaceable parts of the plug will be reset in a radially projecting direction outside the plug, causing the plug to engage in the sleeve of the next valve of an outlet branch and thus to open the valve. As soon as the plug has left the sleeve of a valve, the valve will be closed by the action of a spring-biased device.
It is a disadvantage of this known fluid distribution system that the plug having an enclosed time relay is rather vulnerable and will be subjected to interruptions, for instance as a result of deposits, so that it no longer operates satisfactorily. As a result, the entire fluid distribution system will become inoperable, whilst additionally the exact location of the plug in the distribution system cannot sufficiently be traced.
It is another shortcoming of the known fluid distribution system that the presence of the time relay enclosed in the plug requires the plug to have a given length with ample bends to prevent the plug from becoming jammed in a bend, whilst furthermore, all the outlet branches constantly receive an equal quantity of fluid due to the action of the plug, so the residence time of the plug in a sleeve of a valve, always remains the same.
It is an object of the present invention to improve on a fluid distribution system of this type, so that the above-described shortcomings are overcome.